1. Field of the Invention
The present invention relates to a slider or head assembly used in such fields as magnetic storage.
2. Description of the Related Art
A hard disk drive (hereinafter referred to as HDD) is a well known magnetic storage. An HDD utilizes a disk as a storage medium. The following is description of the case where a disk is used as a storage medium.
In the field of HDD, storage capacity is rapidly increasing. Storage media (hereinafter referred to as disks) and magnetic heads are being developed to cope with this high storage capacity. The magnetoresistive head (hereinafter referred to as MR head) is well known as a magnetic head that copes with high storage capacity.
An MR head that copes with high storage capacity is being manufactured with a track width on the order of several microns. Further, storage capacity is increasing at a rate approaching 5 Gb/in2. A tracking operation in an HDD involves moving an MR head-equipped slider in a track on a disk and reading magnetic signals recorded on that track. In this tracking operation, a method is used whereby the slider is held by a suspension, and this suspension is driven by a voice coil motor.
The assembly that joins a suspension to a slider that positions an MR head is called a head assembly. A conventional example of this head assembly is described.
An HDD is provided with a voice coil motor (hereinafter referred to as VCM) near the base of the suspension. The VCM drives the suspension, and controls the position of the slider mounted at the tip of the suspension. The magnetic head is positioned above a track on a disk by controlling the position of the slider.
A track of several xcexcm or less in width is provided on a disk, and the tracks are in close proximity to one another.
A slider has a flying surface that faces the disk. When the disk rotates, an airflow is produced between the slider flying surface and the disk, generating a force that causes the slider to float above the disk. In this manner, the MR head provided on the slider magnetically records information on the disk, and/or reads magnetically recorded information from the disk.
An increase in storage capacity affects recording and reading accuracy. Disk track width becomes narrower in line with increased storage capacity. As a result of this, finer tracking operations are required. Therefore, in this tracking operation, the MR head must be accurately moved to a micro-track region.
A tracking operation, as described above, means moving an MR head built into a head assembly to a track region by driving the head assembly suspension by using a VCM. However, because the accuracy of VCM-driven movement is limited, it is impossible to achieve high positioning accuracy.
With a low-positioning-accuracy tracking operation, the MR head is affected by an adjacent track, resulting in a heightened noise level. A rise in the noise level causes a drop in read-write accuracy.
Further, because the drive of the VCM is transmitted to the MR head via the suspension, it is not possible to drive the MR head with a high speed of response. When the head assembly drive speed is slow, it is impossible to speed up the overall write operations and read operations of an HDD, even though the signal frequency of the electronic circuit, which processes the write signals and read signals, is increased.
Conventional technology, which attempts to solve for the above-mentioned problems, is described below.
FIG. 14 is an oblique view showing a schematic of a head assembly disclosed in xe2x80x9cINVAR MEMS MILLIACTUATOR FOR HARD DISK DRIVE APPLICATIONxe2x80x9d on pages 378-382 of IEEE Catalog Number 97CH36021, and xe2x80x9cANGULAR MICROPOSITIONER FOR DISK DRIVESxe2x80x9d on pages 454-459 of the same catalog.
FIG. 14 shows a head assembly comprising a slider 901 having a flying surface 911, an actuator 902, a suspension 903, and an MR head 12.
The actuator 902 has a movable portion 922 on a substrate, as shown in FIG. 15, which is a cross-sectional view of the C-Cxe2x80x2 portion of FIG. 14. The actuator 902, rotating or linearly moving the movable portion 922, performs tracking by rotating or linearly moving the slider 901.
That is, with this technology, in addition to using a VCM to move (with rough movement) the MR head via a suspension, an attempt is made to enhance drive accuracy by mounting an actuator 902 to the slider 901 and utilizing this actuator 902 to refine the movement of the MR head.
Furthermore, when describing this technology, the drive portion 921 of the actuator 902 is affixed to the slider 901 side, while the movable portion 922 is affixed to the suspension 903 side. The rotating movement or linear movement of the movable portion 922 causes the slider 901 to rotate or to move linearly. The movement of the slider 901 implements the tracking of the MR head 12 with good accuracy at the prescribed position.
The problems that arise with the technology illustrated in FIGS. 14 and 15 when attempts are made to further increase storage capacity are described here.
As, in this prior art, mounted on top of the slider 901 is an actuator 902, which has a drive portion 921 and a movable portion 922 to move the MR head 12, the overall thickness and weight of the head assembly (in this prior art, this assembly comprises a slider 901 with an MR head, a suspension 903 and an actuator 902) increases by the amount of the actuator 902, and the center gravity is heightened.
The reading of a signal recorded on a disk is performed via the following operation. A slider of floating type is moved at high speed above the track to be read on a rotating disk. Hereinafter, the movement of this slider is called a seek operation. A sensor portion provided on the slider reads the magnetic storage recorded on a track. The slider is controlled so that the flying height, which is the distance between the built-in sensor portion and the disk, is constant.
A high center gravity position of a slider causes the slider to sink. A large slider sink results in larger angle of inclination of the slider flying surface which faces the surface of the disk. A large slider sink makes it impossible to control the flying height in a consistent manner. The problem is that a change in the flying height of a slider at seek causes the slider to make contact with the disk, damaging the disk. There is also the problem that a change in the flying height of a slider during reading generates noise.
Further, there is the problem that an increase in the weight of a slider increases the inertial force applied to the tip of the head assembly at seek, making tracking difficult.
A disk array HDD is formed by stacking a plurality of disks, a plurality of heads and a plurality of suspensions. In a disk array HDD, the distance between a slider""s flying surface and a suspension is the sum of the respective thicknesses of the slider, head and suspension. An increase in the thickness of each component increases the spacing between the disks, increasing the thickness of the HDD. An increase in the thickness of the HDD makes it difficult to incorporate the HDD into equipment such as portable personal computers, which are required to make the overall thickness thinner.
An object of the present invention is to design a head assembly of the type that has an actuator built into the slider so as to curb the weight and thickness thereof.
The present invention makes the thickness of the slider partially thinner, forming a thin plane portion. The plane portion is formed by a step portion or a flat portion on the slider. The head assembly is configured by joining an actuator to the thin plane portion. This configuration makes the thickness of the assembly that joins together the slider and the actuator substantially thinner. The present invention prevents increases in the thickness and weight of the tip of the head assembly, and stabilizes flying characteristics.
The plane portion is formed on the surface of the side opposite the flying surface of the slider. The plane portion is used as the support surface, which supports the actuator on top of the slider. A convex portion is formed on the same surface as the plane portion. The convex portion is used as a positioning member when joining the actuator to the slider. The convex portion and the plane portion join the actuator to the slider with high positional accuracy. High positional accuracy joining prevents the relative relationship between the amount of drive of the actuator and the amount of movement of the sensor portion provided in the slider from varying in accordance with the product.
For a first slider according to the present invention, the surface of one side thereof is the flying surface, and the surface on the opposite side of this surface forms a step, and the upper surface of the portion that becomes lower by the formation of this step becomes the surface for storing or mounting an actuator.
Furthermore, a protective member enclosing a sensor portion is mounted to this slider. This sensor portion is positioned in close proximity to the flying surface. The step portion is formed separate from the protective member enclosing the sensor portion, and the actuator is provided in the plane portion of the step portion. The portion of the sensor portion facing the storage medium is exposed, and the other portion is enclosed in the protective member.
The step portion is formed by a step, indent, slot, or notch formed in the surface of the slider opposite the flying surface. It is desirable for the step portion to provide a flat bottom surface or plane for joining the actuator. In joining the actuator and the slider, it is desirable that the thickness of the slider and actuator assembly when the actuator is joined to the step portion be smaller than the dimensions achieved by adding the respective thicknesses of the slider and actuator. Furthermore, the separation of the protective member and the step portion makes it possible to count on the effect whereby the strength of the protective member is not lost when the step portion is formed by cutting work, and also makes it possible to maintain the strength of the slider, and to relieve strain.
Instead of a configuration, wherein the sensor portion is enclosed in the above-mentioned protective member, it is possible to use a configuration, wherein it is embedded within the slider with one part exposed.
For a second slider according to the present invention, the surface of one side thereof is the flying surface, and the surface on the opposite side of this surface is a flat surface, and a positioning member of a prescribed width and prescribed height for positioning an actuator is affixed to the top of this flat surface.
Furthermore, a protective member enclosing a sensor portion is mounted to this slider. This sensor portion is positioned in close proximity to the flying surface. Further, an actuator is provided on the flat surface. Installing the actuator to the flat surface of the slider makes it possible to reinforce the strength of the thin slider. The portion of the sensor portion facing the storage medium is exposed, and the other portion is enclosed inside the protective member.
The positioning member is formed using a lug or convex portion, and the actuator is affixed by bringing it in contact with this lug or convex portion. The positioning of the actuator relative to the slider is performed by bringing the actuator in contact with the lug or convex portion.
It is desirable to maintain the mechanical strength of the slider and actuator assembly by joining the actuator to both the flat surface of the slider and the positioning member. Further, the positioning member can be utilized as a mark for measuring the relative position of the actuator with regard to the slider. The positioning member can be configured as part of the slider, or it can also be configured as a separate member, which joins to the slider.
For the present invention, it is desirable that the joining of the slider and the actuator be carried out using a conductive adhesive between the two members. Joining via a conductive adhesive connects the slider to the actuator electrically. Further, the actuator and the suspension are also connected electrically. Static electricity that builds up in the slider or actuator can escape to the ground via the suspension, and this ground can prevent the dielectric breakdown of the MR head.
The actuator of the present invention comprises a movable portion and a drive portion on a substrate. The drive portion is the component that drives the movable portion, and it is desirable that it generates an electrostatic or electromagnetic driving force. Furthermore, as for the actuator substrate, it is desirable that the length or width thereof be around 0.3-1.5 mm.
For the present invention, it is desirable that the thickness of the assembly of the slider and actuator be in the range of 0.2-0.65 mm. The assembly thickness refers to the sum of the thickness of both the parts of the slider and actuator, which are joined together, and the thickness of the adhesive applied between these parts.
For the present invention, an MR head, optical head or magneto-optical head can be utilized as the sensor portion. The sensor portion is provided in close proximity to the flying surface. The meaning of this term close proximity includes the situation wherein at least a part of the sensor portion is on the same plane as the flying surface, the situation wherein at least a part of the sensor portion is on the same plane as the flying surface by way of an overcoat film, which covers the flying surface, and the situation wherein the sensor portion and flying surface are separated within a range wherein the sensor portion can read the signals on the disk.
The slider and head assembly of the present invention join a suspension to the side of the slider that is opposite the side to which the actuator is joined. In the head assembly, preferably, the actuator comprises a substrate and a movable portion, the actuator substrate is joined to either the step portion of the first slider or the flat surface of the second slider, and the movable portion of the actuator is joined to the suspension. Even more preferable, it is assumed that by intervening a conductive adhesive at two actuator joining areas, it is possible to prevent the electrostatic charges that occur between the actuator and the suspension or slider.
For the present invention, the sensor portion and actuator have electrode portions, and the suspension has a wiring portion. Each electrode portion is electrically interconnected to corresponding components of the wiring portion by bonding wire. As the electrode portion, metal pads or metal terminals, and the end of a conductive film can be used. On the other hand, as the wiring portion, covered lead wire or flexible printed-wiring can be used.